Fabric venetian blind and method of fabrication

ABSTRACT

A method of making a fabric Venetian blind comprises helical winding of a narrow, elongated strip, which, when properly overlapped and bonded along longitudinal glue lines, will form the vanes and front and rear facings of the blind. The strips may be formed of a single, uniform material, or of adjacent, longitudinally extending portions of relatively opaque and relatively translucent fabric. An alternative embodiment uses the same winding technique to similarly form a structure of only translucent fabric, but with pockets for subsequent insertion of opaque vanes. Several alternative strip configurations and assembly arrangements are disclosed. The disclosed method and structure may also be used to form products for other applications.

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 09/288,389, filed Apr. 8, 1999, which is a continuation-in-part ofU.S. patent application Ser. No. 08/947,608, filed Oct. 9, 1997.

FIELD OF INVENTION

[0002] This invention relates to window coverings, and more particularlyto the field of Venetian blinds having front and rear panels of sheer ortranslucent fabric between which are arrayed a series of relativelyopaque fabric slats or vanes which can be tilted for light control bymeans of limited rotation of a wind-up roll to which the front and rearpanels are connected. The invention includes an improved product,fabricating technique and apparatus for fabricating such blinds, whichtechnique can also be applied to forming multi-layered composite sheetsused in other types of products and for other purposes.

BACKGROUND OF THE INVENTION

[0003] The most familiar type of Venetian blind window coveringcomprises a series of rigid slats or vanes suspended and controlled by aladder cord system. The slats are typically wood, plastic or metal, andrest on the ladder cord rungs. The rungs are secured to front and rearvertical cords whose upper ends are secured to circumferentially spacedlocations on a wheel. Limited rotation of the wheel, by means of acontrol wand or cords, causes relative motion between the front and rearcords, which in turn tilts the rungs and vanes. The entire array can beraised and lowered by additional cords which act to lift a bottom rail.

[0004] A modified type of Venetian blind is disclosed in U.S. Pat. No.3,384,519 to Froget. There, the ladder cord system is replaced by frontand rear cloth panels to which the vanes are heat welded. Preferably,the cloth panels and vanes are all made of thermoplastic yarns, tofacilitate bonding by heat welding. Partial rotation of an upper drum,to which the panels are connected, shifts the panels relative to eachother, thereby causing the vanes to tilt for light control. Anothersimilar product is disclosed in French Patent No. 1,521,488 to Demerson.Demerson prefers films to woven fabrics, and discloses adhesive bondingof the vanes to the facing panels.

[0005] Several more recent patents are directed to modifications ofFroget's basic idea, wherein the vanes are made of flexible fabric,adhesively bonded to the front and back panels. Additionally, the entirearray can be retracted from the window opening by winding it onto anupper wind-up roller by means of cords which lift a bottom rail.Representative of these patents are U.S. Pat. Nos. 5,287,908, 5,313,999,5,320,154, 5,394,922 and 5,456,304, all assigned to Hunter Douglas,Inc., and a patent to Ren Judkins patent, U.S. Pat. No. 5,339,882.

[0006] U.S. Pat. No. 5,664,613 (and subsequently assigned to a companyowned by the assignee of the present application) describes another formof construction for a fabric Venetian blind. A continuous panel ofrelatively translucent material forms one facing of the blind. To thatpanel is bonded a series of parallel fabric strips at uniform intervals.Each strip comprises two adjacent portions of dissimilar material, onebeing relatively translucent and the other relatively opaque. The freeedge of the opaque portion is bonded to the facing panel, while the freeedge of the translucent portion is bonded to the adjacent strip at thejunction line of that strip's two portions. The assembled translucentportions of the constituent strips become the second facing panel of thecompleted blind. That is, the second facing panel, rather than being asingle continuous panel of fabric, is a composite of several parallelstrips, each having a height dimension approximately equal to the width(or depth) of the vanes.

[0007] U.S. Pat. No. 5,888,639, assigned to Newell Operating Co.,discloses in FIGS. 15-19 a fabric Venetian blind having a structure verysimilar to that disclosed in FIGS. 3-6 of my parent application, Ser.No. 08/947,608, filed Oct. 9, 1997 (which Figures are also found in thepresent application). As in my parent application, the product is alaminated assembly of previously formed three-element strips. However,the relationship of the individual components of each three-elementstrip, and the method of preparing each such strip for subsequentassembly to adjacent strips, is substantially different. Furthermore,the method of assembly of the three-element strips to each other issubstantially different, in that the strips are cut to a predeterminedlength, prior to their lamination to each other, which lengthcorresponds to the desired width of the fabric Venetian blind. Themethod of assembly disclosed in my parent application and herein,wherein the three-element strip is helically wound upon itself inpartially overlapping successive layers, represents a substantialimprovement in the speed and economy of manufacture.

[0008] U.S. Pat. Nos. 5,490,553 and 5,603,369, assigned to HunterDouglas, disclose in FIGS. 16-19 a vertical blind wherein each verticalblind vane is formed of the same strip of material as an adjoiningportion of a facing panel on one side of the vanes. The single facing isa composite of narrow vertical strips. The vane portion of this strip isdoubled back on itself. Another patent assigned to Hunter Douglas, U.S.Pat. No. 5,638,880, discloses in FIG. 26 a vertical blind wherein thefacing on one side of the vanes comprises a series of vertical strips ofmaterial, each joined along one vertical edge to an adjacent strip, andat the other vertical edge to both the adjacent facing strip on thatside and a discrete piece of substantially rigid, planar materialforming the vane. The patent further discloses that both a front and arear facing may be fabricated of such strips, and the strips and vanescan be oriented in either the vertical or horizontal directions.

[0009] U.S. Pat. No. 4,631,217, also assigned to Hunter Douglas,discloses in FIG. 2 a honeycomb or cellular type of window coveringwherein a series of pleated, generally Z-shaped strips, each formed of asingle piece of fabric, are bonded together in a manner whereby eachstrip forms the front portion of one cell, the rear portion of anadjacent cell, and a dividing wall between the two cells. The dividingwalls, however, are incapable of functioning as the vanes of a Venetianblind type of product, because they remain substantially perpendicularto the front and rear faces of the window covering throughout the fullrange of expansion and collapse of the cells.

[0010] Known processes for manufacturing these prior art fabric Venetianblinds are complex, slow and costly, and have contributed to a highprice for these otherwise attractive products.

[0011] Accordingly, it is a principal object of the present invention tocreate additional alternative three-element or multi-element stripconfigurations and bonding procedures which also lend themselves to theuse of the more economical helical winding technique disclosed in myabove-mentioned parent application.

SUMMARY OF THE INVENTION

[0012] The presently contemplated application for the disclosedinvention is the formation of fabric Venetian blinds, using a techniqueof helically winding an elongated strip of fabric. In one embodiment ofthe Venetian blind, a three-portion strip is initially formed from threeside-by-side, longitudinal, bands or portions of approximately equalwidth and length. Each edge of the central portion is joined byultrasonic welding to an edge of the adjacent outer portion. The outerportions are formed of sheer or relatively transparent material, and thecentral portion is relatively opaque.

[0013] As a result of the helical winding process, the central portionbecomes the blind vane, while the two outer portions ultimately becomesegments of the front and rear composite facings of the blind.Successive windings are staggered and partially overlapped so that twoof the three portions of the underlying winding are covered by theoverlying winding. Two longitudinally extending glue lines are appliedalong the underside of the infeeding overlapping strip, these beingpositioned to bond together adjacent windings. A tube-like woundstructure is formed which, when cut open along a line perpendicular tothe helix angle, will result in a fabric Venetian blind. The disclosedmethod of fabrication thus differs significantly from the prior art.Indeed, this product and its benefits could not so economically beachieved by known manufacturing processes.

[0014] The strips, once assembled by the winding operation, produce boththe flexible vanes and the front and rear face panels in a singlecontinuous process. The resulting composite face panels comprise narrow,horizontal strips which have been joined successively to one another inthe winding operation. The resulting flexible vanes swing betweenlight-admitting and light-blocking positions upon relative movementbetween the two composite face panels.

[0015] Alternative constructions may include an additional layer offabric in the vane portion, to create a pocket into which an opaqueinsert can subsequently be inserted, and the formation of productshaving multiple rows of vanes or central ligaments.

[0016] Another alternative construction relates to a modifiedthree-element strip configuration wherein the entirety of one sheerstrip more fully overlaps the relatively opaque vane strip, with oneedge substantially aligned with a first edge of the vane andultrasonically welded thereto, while the other sheer strip is slightlylapped under and ultrasonically welded to the second edge of the vane.The vane is slightly wider than each of the sheer strips, permitting thevane to be simultaneously welded to each of the sheers withoutinterference by overlapping the other sheer at the desired weld zone.

[0017] The novel winding technique disclosed herein may also be used tofabricate products from other types of materials or intended for otherfields of use. For example, multi-layered materials made from thermallynon-conductive or reflective material may be made for insulationapplications; polarized or tinted films may be used to create desiredoptical effects; and materials of selected porosity may be used to formair filtration products.

[0018] Also disclosed is the use of a resiliently deformablecircumferential surface on a nip roll which functions to steer thesheet-like material which is driven by the roll set when differentialpressure is applied to the two ends of the deformable roll.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1A is a simplified perspective view of the fabric Venetianblind of the present invention, shown with the vanes positioned in theirmaximum light-admitting setting.

[0020]FIG. 1B is a view similar to FIG. 1A, showing the vanes positionedin a partially closed setting.

[0021]FIG. 2 is a side view, in simplified form, of a representativeprior art fabric Venetian blind, wherein the vanes are joined to single,continuous-sheet type front and rear sheer panels. The blind is shown inthe fully-open position of the vanes, while a partially closed positionis shown in phantom lines.

[0022]FIG. 3 is an enlarged fragmentary side view of the blind of FIG.1A.

[0023]FIG. 4 is an exploded schematic view of the blind of FIG. 3,showing the relationship of adjacent three-portion strips.

[0024]FIG. 5 is an enlarged, simplified view of the blind of FIG. 3,with the vertical scale exaggerated to reveal the relationship ofadjacent three-portion strips.

[0025]FIG. 6 is a perspective view of a fragment of a three-portionstrip such as used in the embodiments of FIGS. 4 and 5.

[0026]FIG. 7 is an exploded end view of a second form of thethree-portion strip.

[0027]FIG. 8 is a view similar to FIG. 7, showing a third form ofthree-portion strip.

[0028]FIG. 9 is a simplified perspective view of equipment suitable forforming a blind according to FIGS. 3-5 using the process of the presentinvention.

[0029]FIG. 10 is a schematic side elevational diagram of the equipmentshown in FIG. 9.

[0030]FIG. 11 is a simplified plan view of the equipment of FIG. 9,showing the supporting framework.

[0031]FIG. 12 is a simplified side elevational view of the equipment ofFIG. 11.

[0032]FIG. 13 is a perspective view of a helically wound tube of blindmaterial, prior to being cut open, viewed from the opposite end of thespars from the end shown in FIG. 9.

[0033]FIG. 14 is a schematic end view, in the direction of the cuttingplane C-C, of the helically wound tube showing how it is cut open toform a full-width fabric Venetian blind.

[0034]FIG. 15 is a schematic elevational view of nip roll set 66.

[0035]FIG. 16 is an end view of the nip roll set of FIG. 15.

[0036]FIG. 17 is a plan view of the nip roll set of FIG. 15.

[0037]FIG. 18 is a view similar to FIG. 5, showing an alternativeembodiment having pockets to receive opaque vane inserts.

[0038]FIG. 19 is a view similar to FIG. 5, showing still anotheralternative embodiment wherein multiple rows of vanes or centralligaments are provided.

[0039]FIG. 20 is a view similar to FIG. 9, showing a modified system forfeeding the fabric strip to the winding equipment.

[0040]FIG. 21 is a view similar to FIG. 9, showing another modifiedsystem for feeding the fabric strip to the winding equipment.

[0041]FIG. 22 is an enlarged, simplified view, similar to FIG. 3, butshowing the configuration which results from a modified location of theglue line which joins successive three-element strips.

[0042]FIG. 23 is an end view, with the vertical scale exaggerated, of aprior art three-element strip configuration.

[0043]FIG. 24 is an end view, similar to FIG. 23, showing one of themodified three-element strip configurations of the present invention.

[0044]FIG. 25 is a fragmentary perspective view, with the vertical scaleexaggerated, of a portion of the helical winding sequence used inconjunction with the three-element strip configuration of FIG. 24.

[0045]FIG. 26 is an enlarged fragmentary side view of the blind whichresults from use of the three-element strips of FIG. 24.

[0046]FIG. 27 is a view similar to FIG. 26, but showing theconfiguration which results from a modified location of the glue lineswhich join successive three-element strips.

[0047]FIG. 28 is a view similar to FIG. 25, but showing the glue linesinitially applied to the opposite element of the opposed elements to bejoined.

[0048]FIG. 29 is a view similar to FIG. 25, but showing a modifiedorientation of the three-element strip of FIG. 24 as the strip is fedinto the helical winding apparatus.

[0049]FIG. 30 is a fragmentary perspective view of a portion of thewinding apparatus adapted for use with the three-element strip of FIGS.24-26.

[0050]FIG. 31 is a fragmentary plan view of a portion of the windingapparatus illustrated in FIG. 30.

[0051]FIGS. 32a-32 b through FIGS. 38a-38 b are end views, similar toFIG. 23, showing additional alternative embodiments of three-elementstrips according to the present invention, and wherein the “a” and “b”figures of each pair show the strip in its flattened configuration afterwelding and in its partially opened, light-admitting configuration (asachieved after assembly with other such strips in a light-controllingproduct, respectively.

[0052]FIGS. 39a-39 b through FIGS. 42a-42 b are end views, similar toFIGS. 32-38, showing still further alternative embodiments, whereintwo-element fabric strips are welded to form a pocket for subsequentreception of an opaque material.

[0053]FIG. 43 is an end view, with the vertical scale exaggerated, of amodified three-element strip configuration of the present invention.

[0054]FIG. 44 is an enlarged fragmentary side view of the blind whichresults from use of the three-element strips of FIG. 43.

DETAILED DESCRIPTION

[0055]FIG. 2 of the drawings shows a fabric Venetian blind 20 which, inits general construction, is typical of the prior art. The solid linesindicate the fully-open position of the vanes. The blind comprises afront facing 22, rear facing 24 and vanes or slats 26. The front andrear facings are each typically formed of a continuous panel of sheermaterial, chosen for its combination of soft, aesthetic appeal, itsability to permit a substantial amount of light to be transmitted whenthe vanes are in their open position, and, depending upon the selectedweave, its ability to permit viewing of scenes through the material. Thevanes are bonded along their respective longitudinal edges to the frontand rear facings. Bonding can be by adhesive or thermal welding. Whenthe wind-up roller from which the blind is suspended is rotatedslightly, the front and rear facings shift in a vertical directionrelative to each other, causing the angle of the vanes to change. Aposition near the fully-closed setting of the vanes is shown in phantomin FIG. 2, with the elements labeled with primed numerals.

[0056]FIGS. 1A and 1B show, in simplified form, the basic elements of acomplete fabric Venetian blind assembly 28 in full-open and near-closedconditions, respectively. The blind comprises front and rear sheer orrelatively translucent facings 30,32, respectively, a plurality ofrelatively opaque vanes 34, a wind-up roller 36 and a bottom rail 38.Not shown are the cords or other means for rotating roller 36 to adjustthe vane angle and to roll the shade around the roller to fully exposeall or a portion of the window opening.

[0057] Comparing FIGS. 1A and 1B it can be seen how the points ofattachment of the front and rear facings to opposite sides of thecircumference of the roller result in relative vertical movement of thefacings, and therefore adjustment of the vane angle, when the roller isrotated slightly.

[0058]FIG. 3 and the following figures illustrate various novel aspectsof the present invention. A first embodiment is best shown in FIGS. 4-6.Fabrication begins with the creation of an elongated strip 40 (see FIG.6) comprising at least two dissimilar fabric materials. The outerportions 30′,32′ are formed of relatively translucent or sheer material,while central portion 34 is formed of a relatively opaque material.Outer portions 30′,32′ may be formed of the same or different fabrics.The central portion can be opacified by use of a more densely wovenfabric, or by coating or laminating (see discussion of FIGS. 7 and 8below) or by the use of opaque inserts (see discussion of FIG. 18below). The adjoining edges of these portions may be connected bygluing, ultrasonic welding, thermal bonding or stitching. Ultrasonicwelding is the preferred method, because it is speedy and permitsprecision location of adjoining edges.

[0059] To accomplish such welds, the strip portions are made to overlapone another in the region to be welded, which overlap is then meltedtogether by a commercially available ultrasonic seam welding device suchas a Seam Master LM 720 or LM 920 manufactured by Sonobond Corporation.By way of example, the overlap may be about 0.10-0.20 inches, with thewelding performed by a stitch-wheel having about one and one-half timesthe pitch of the main knit, in order to assure fiber capture. Acontinuous (rather than stitch knit) will also work if the vane isnon-woven or film material. This process also beneficially compressesthe welded zone and destroys the fabric interstices, so that the jointwill not be porous to subsequently applied glue lines. Thus, unsightlybleed-through of the glue lines is avoided. The width of strip 40 isapproximately three times the desired vane width (i.e., blind thicknessin the fully open setting of the vanes). It should be noted that theillustrations of FIGS. 4-6, for simplicity, show the three-elementstrips as if they are each an entirely coplanar composite structure,without_overlapping junctions at the adjoining edges of their individualcomponent strips,. In practice, it is preferred that the vane overlapsone sheer and underlaps the other sheer, with the strips beingoverlapped with adjacent three-element strips so that the sheer of onestrip overlaps and is directly glued to the sheer of the preceding andsucceeding strips.

[0060] Unlike known processes of the prior art, the fabric Venetianblind of the present invention is generated by helically winding thestrip upon itself, in partially overlapping fashion, with each windingbeing bonded to the preceding winding along uniformly locatedlongitudinal bonding lines. The result is that each winding of stripmaterial 40 constitutes one vane and an adjacent fragment of each of thefront and rear facings of the completed fabric Venetian blind.

[0061] The relationship of adjacent windings of strips 40 of this firstembodiment is best seen in FIGS. 4 and 5. Each strip winding 40 overlapsapproximately two-thirds of the preceding strip winding. Specifically,the leading edge (i.e., the right edge as viewed in FIG. 6) of a windingis placed at or near the sheer/opaque junction of the preceding winding.A previously applied front glue line 42 is located on the underside ofthe upper strip at that contact line, while a previously applied rearglue line 44 is located at the underside of the upper strip at or nearthe junction between the rear sheer portion 32′ and the opacified vaneportion 34. That rear glue line 44 will then join such strip to thetrailing edge of the previously wound or lower strip 40.

[0062] The choice of location of glue lines 42 and 44 relative to thejunctions between the sheer and relatively opaque portions of eachwinding is not critical. FIG. 22 shows the identical three-element stripillustrated in FIG. 5, but with the front and rear glue lines 42″, 44″,respectively, shifted laterally away from the junction between therespective sheer and relatively opaque portions of each three-elementstrip. That relocation of the glue lines creates short tab-likeextensions 43″, 45″ of the respective sheer portions, which tabs projectinto the interior of the cells defined by the sheers and vanes.

[0063] Initial indications are that these tab-like extensions 43″, 45″appear to be beneficial. Fabric Venetian blinds which have the vanematerial connected essentially directly to the planes of the front andrear facings have a tendency not to fully close in the overlapping,light-blocking position. This phenomenon appears to result from the“memory” which the vanes retain of their shape in the open position.However, the optional use of sheer tabs 43″, 45″, resulting fromrelocation of the glue lines, places much less resilient sheer materialin these flexing or hinging zones. The reduced memory and/or resilienceof the sheer material allows the relatively opaque vanes to lay flatlyagainst the faces, even if there is some residual splay in the weldjoints. This benefit is even greater where the tab extends in thereverse direction from the vane, as in the case of the upper tabs shownin FIG. 27 as compared with the lower tabs of that Figure.

[0064] Furthermore, if the extreme edge of the center opaque vane(outboard of its weld to the sheer tab) overlays the sheer tab to asubstantial degree, as is typical, then the reverse-style tabbeneficially acts as a buttress against the facing when the vanes arepulled into the open, view-through position. The Vane must then adoptgreater transverse flex and curvature, which is an established aestheticbenefit, rather than locally hinging as a stiff and flat element fromthe facing at the much softer sheer tab.

[0065] As exemplified by the configuration of FIG. 22, the relativelyopaque portions need not fully span the distance between the front andrear facings, as long as the opaque portions overlap when the blind isin the fully closed position. Glue lines 42 and 44 may be spaced fromthe exposed, exterior edges of the strips, if desired, as when a seriesof unsupported, fringe-like bands are desired on one or both of thefacing panels.

[0066] Alternative forms of the three-portion strip 40 are shown inFIGS. 7 and 8. In FIG. 7, the strip is formed of a full-width relativelytranslucent portion 46, with a relatively opaque central portion 48laminated to it by any of the previously described joining techniques.This embodiment is not preferred, because it tends to be too stiff tohang uniformly. In the FIG. 8 embodiment, the three-portion strip isformed of a single piece of fabric, but with less dense weaving patternsbeing used for the outer portions 50, and a more dense or opaque weavingpattern being used for the central portion 52 which will become the vaneof the finished blind. The embodiments of FIGS. 6 and 8 are preferred,because they tend to hang in a more uniform, wrinkle-free manner.

[0067] The method and equipment employed for fabricating the embodimentof FIGS. 3-5 is illustrated in FIGS. 9-17 of the drawings. Themanufacturing equipment includes a pair of parallel, non-rotating spars56,58 skewed at an angle to two parallel nip roll sets. The first niproll set 60 serves to drive the fabric by tensioning the upper reach offabric tube 88. Nip roll set 60 comprises a lower, motor-driven roll 60and an upper, pressure roll 62. The second nip roll set 66 serves toprovide tensioning drag and to steer fabric tube 88. It comprises alower, motor-driven roll 68 (which is driven in a manner to tension orbrake the span of fabric between it and drive nip roll set 60) and anupper, steering pressure roll 70. The steering action is describedbelow. Rolls 62 and 68 may be driven by belt-driven sprockets (notshown). The fabric between nip sets is thus held flat and substantiallyplanar for attachment of the infeeding strip, assuring that the finalproduct will also lie flat.

[0068] The three-portion fabric strip 40 is fed from strip supply roll72, which has its own drive motor M which drives roll 72 at a speedcontrolled by the position of dancer 73. If the strip loop around dancer73 gets smaller, the motor driving roll 72 speeds up to maintain auniform amount of strip in that portion of the strip feed system. Strip40 continues from dancer 73 through a nip roll set comprising upper roll74 and lower motor-driven roll 75 to tension-sensing roll 76, which isprovided with a load cell on its axle. This load cell senses tension inthe strip between rolls 76 and 64, and adjusts the speed of motor Massociated with nip roll 75 to maintain the desired tension in thatportion of the in-feeding strip.

[0069] Two adjacent glue applicators 78 apply continuous beads of glue42,44 to strip 40.

[0070] The support structure for the two pairs of nip rolls 60,66comprises main mounting plate 80 (see FIGS. 11-12) and end plate 82connected thereto by cantilevered beams. End plate 82 supports the endof upper rolls 64,70 remote from main plate 80, while lower rolls 62, 68are supported by similar cantilevered beams and end plate 82′. These endplates must be supported in this fashion so that no support structurecrosses from inside to outside the fabric loop or tube 88 defined byspars 56, 58. Spars 56,58 are cantilevered from a separate framestructure 84, which can be pivoted about vertical axle 86 to permit thespars to be set at a predetermined angle relative to the two nip rollsets. This angle is a function of the desired lead angle for the helicalwinding of strip 40, as will be explained below. Appropriate clearanceholes are placed in frame 84 to permit passage of spars 56,58. The endof cantilevered spars remote from mounting frame 84 is free ofconnection to supporting structure to permit removal of the continuouslyformed fabric tube therefrom and to allow adjustment of the spar anglerelative to the lower rolls. Alternatively, if spar angle adjustmentwere deemed unnecessary, the ends of the spars could be attached to thelower roll support or to any other structure lying entirely withinfabric loop 88. Alternatively, the spars can extend far beyond thelongest desired window shade and be supported to ground at both ends. Inthat case, the fabric tube must be cut open as described below to removethe fabric product from the spars.

[0071] As best shown in FIG. 9, the process begins with thethree-portion fabric strip 40 being pulled from supply roll 72 by drivenip roll set 74-75. Controlled feed rate of the strip between supplyroll 72 and nip roll set 60 is provided by motor-controlling signalsfrom dancer 73. Constant tension in the strip between nip roll set 74-75and drive nip set 60 is provided by motor-controlling signals fromtension-sensing roll 76, as explained above. The strip is directed pastglue applicators 78, and the upper, glue line-bearing side of the stripis inverted by roller 76 so that such glue lines come face-to-face withthe preceding winding between the rolls of nip roll set 60. There, theglue joint is closed and the overlapping windings are bonded to eachother.

[0072] As will be appreciated by reference to FIG. 5, the infeedingstrip 40, with glue lines 42, 44 already applied by applicators 78, mustprecisely register with the preceding winding traveling on the upperreach of the fabric loop extending from spar 58, through drag nip rollset 66 to drive nip roll set 60, where infeeding strip 40 first comesinto contact with the preceding winding for bonding. FIG. 9 shows howthe skewing of spar 56 causes the lower reach of the endmost fabricstrip winding to shift laterally as it travels to spar 58 and back tothe point between the rolls of drive nip roll set 60 where the incomingstrip, with freshly applied glue strips 42,44 on its underside, ispressed against it. The lateral shift, a result of the helix lead angle,is selected to cause a shift of approximately one-third of the width ofstrip 40, so that glue lines 42,44 will register with the previouswinding as shown in FIG. 5. Thus, the required relative positioning ofthe relatively opaque vane portion 34 with the relatively translucentfacing portions 30′,32′ will be achieved when the vanes of the finishedblind are placed in their light-blocking or fully closed angularsetting.

[0073] Precise control of the amount of overlap between successivewindings is provided by two independent controllers. First, the lateralposition of infeeding strip 40 from supply roll 72 is provided by acontroller (not shown), or other known web guiding device, whichlaterally shifts the placement of roll 72 along its rotational axis.

[0074] Secondly, additional control of registration of the overlappingwindings of strip 40 is provided by drag nip roll set 66, which has a“steering” capability. Both pressure rolls 64 and 70 are rubber-coated,to provide a compressible surface. Unlike pressure roll 64 of drive niproll set 60, which has a constant force pressing it downward towarddrive roll 62, steering pressure roll 70 has independently controllabledownward pressure (described below) applied at its opposite ends. Whenthe applied pressures are equal at both ends of roll 70, the roll has astrip-contact zone of uniform width along its entire length, where therubber roll is deformed about the unyielding surface of roll 68. Thepassing fabric strip does not deviate from its straight-line path, andcontinues to take the shortest route from spar 58 to nip roll set 60. Anincrease in the nip pressure at one end of roll 70 increases theconcavity of its rubber-coated surface as it is deformed by thecylindrical contour of the non-yielding surface of lower roll 68. Thepath of the fabric strip at that end of the roll lengthens as it isforced to assume the longer curved shape of the further deformed surfaceof roll 70. That is, the strip-contact zone (at that end) between theopposed rolls of nip roll set 66 increases to a greater segment of anarc about the rigid roll's surface resulting from the extra deformationof the surface of roll 70 straddling a lengthened portion of theperimeter of lower roll 68. The resulting longer strip path on the edgewith increased steering pressure creates increased strip tension on thatedge, pulling or steering the fabric toward that edge. Reducing pressureat one end similarly reduces the path there relative to the nominalcondition, drawing the web toward its other edge.

[0075] FIGS. 15-17 schematically illustrate a steering control systemfor varying the pneumatic pressure applied to cylinder P1 on one end ofpressure roll 70. That end of pressure roll 70 is mounted in verticallyslideable bearings. The control signal is provided by a proportionalvoltage output device in the form of an edge-position sensor 92, whichmay be in the form of a linear array of light-emitting outputs andphotocells on opposite sides of the plane of the passing fabrics. Anydeviation from the desired edge position of the strip generates acorresponding deviation from a nominal pressure-demand voltage signalsent by sensor 92 to control computer/proportional regulating valve 94.Valve 94 bleeds or supplies air pressure from source 96 as required tomaintain a desired cylinder pressure defined by the voltage signal. Theresulting tilting and deformation of roll 70 is shown in exaggeratedform in FIGS. 15-16, and the corrected path of the upper reach of fabrictube 88 is shown in the plan view of FIG. 17.

[0076] While the use of crowned rolls to “steer” a web or flat belt to acentral position, and the use of flared-end rollers to spread andde-wrinkle a web, are well known, it is believed that the use of aselectively deformable roller at a nip to steer a web by local controlof path length is novel. Those skilled in the art will recognize thatsteering can be achieved either by varying the pressure on both ends, ormaintaining nip pressure constant on one end while increasing ordecreasing the pressure on the other end, as required.

[0077] Because fabric strip 40 has a helix lead angle as it winds ontospar 56 (which is skewed by such angle relative to drive nip roll set60), the fabric “tube” 88 continuously advances toward the opposite endof the non-rotating spars. The spars, which do not rotate, are highlypolished to facilitate this sliding movement without damage to thefabric.

[0078] The spars are preferably sufficiently long to permit them to holdan entire tube formed from a feed roll. For example, a machine has beenbuilt with twelve-foot long spars, for use with a three hundred-yardlong feed roll. The spars may be perforated to permit pressurized air toprovide an air bearing to reduce the drag of the fabric tube as itadvances along the spars. When the machine is shut down to install afresh feed roll, the tube may be cut off, using a scissors, by firstcutting around the circumference of the tube, generally along a givenstrip. Alternatively, a razor knife may be plunged through thestill-forming tube, just beyond the ends of nip sets 60, 66, and held inposition for one full rotation of the tube. Then the knife is drawnquickly across the severed winding to separate the formed length of tubedownstream from the still-forming tube upstream. The separated tube isthen slid away along the spars and cut open along line C-C while themachine continues to form more tube. Then, the severed tube, while stillhanging on the spars, is cut along a line C-C (see FIGS. 15-16), whichis perpendicular to the edge of the windings, so that the tube may belaid open to form a parallel-edged flat form or slab 90 with the woundstrips perpendicular to the parallel edges. If an automatic splicer isfitted to the supply roller 72, the operation of the machine can be thusmade continuous.

[0079] In the presently constructed machine, the cut open product slab90 is about ten feet wide and about ten or more feet long. The fabricslab is then cut to size for particular windows, and the fabric Venetianblind is fully formed except for its connection to a wind-up roll andassociated hardware.

[0080] Many different products and visual effects can be achieved by useof the present invention. A basic Venetian blind may preferably beformed of polyester (for strength and UV resistance) knitted mesh frontand rear, of different mesh patterns, and a knitted polyester relativelyopaque fabric for the vanes. Where minimization of the moiré effect isnot a primary concern, the same fabric may be used for the front andrear facing panels. A preferred fabric is a stabilized tricot of 28 gage20/1 semi dull polyester, manufactured by Gehring Tricot Corporation,and identified as P201. Stabilized tricots provide a preferredcombination of visual sheerness with a high degree of structuralstability for ease in handling during manufacture. Where moiré effectminimization is a concern, then such fabric may preferably be pairedwith a rear facing fabric in the form of a diamond tulle, such as 36gage, 20/12 bright polyester, manufactured by Gehring, and identified asP1732. The relatively opaque vane may be a jersey fabric, 70/33, 20/1semi-dull textured polyester, like that manufactured by Native Textiles,and identified as P7020.

[0081] A significant advantage of the use of the helical strip-windingtechnique of the present invention is that the resulting front and rearsheer panels, being composites of multiple, narrow, horizontallydisposed sheer strips, tend to suppress objectionable moiré effectswhich would arise if the same choice of fabrics were used in the form ofsingle-sheet, continuous panels for the entire front and rear facings.Tricot type fabric, a preferred form of weave, has heavily barredpatterns extending in the longitudinal or “machine direction” of thefabric as it is manufactured. When such barring is oriented in thevertical direction (of a normally hanging window shade) for continuousmanufacture of single panel facing, a cross-grid pattern is establishedwith the horizontally oriented vanes and vane shadows, leading to arelatively dramatic and objectionable moiré effect. With thestrip-winding technique disclosed herein, the sheer strips andassociated machine-direction bars of the tricot fabric can be orientedhorizontally. In this orientation, the barring pattern does not form across grid with the vanes, but tends to blend in with the parallel vanesand vane shadows. Also, the multiplicity of narrow sheer strips acts tobreak up otherwise large-scale moiré patterns into smaller, morelocalized, banding patterns which are less objectionable. Still further,the individual sheer strips tend to be slightly tilted or bowed relativeto each other, rather than more truly parallel, as in the case facingpanels formed of single, continuous sheets. This fact, along with small,local differences in tension and alignment of individual threads inadjacent wraps, further diminishes large scale coherence in the moiréinterference patterns.

[0082] Alternatively, other knits, wovens or nonwovens may be used foreither the facings or vanes, and hot-melts, pressure sensitives, tapesor other adhesives may also be used, provided they possess UVresistance, non-yellowing and strength with no flow at up to 200 degreesFahrenheit for durability in sunlit windows.

[0083] While many of the known glues can be used, hot-melt adhesives arepreferred, such as the high-temperature polyester manufactured by Bostikand identified as 7199 or W4360B. This type of adhesive is advantageousbecause of the ability to be precisely metered through applicationnozzles, high initial tack, rapid cure to a flexible final state,ultraviolet resistance for use in sunlit windows and minimum ofbleed-through adhesion as a result of the rapid cooling of its surfaceonce applied. Alternatively, moisture-cure polyurethane hot-appliedglue, such as HL-9608 manufactured by H. B. Fuller, has many of the samefeatures, plus added strength and flexibility once cured, but thesebenefits must be considered in light of slower curing and associatedbleed-through tendencies.

[0084] Another alternative Venetian blind product which may be formed bythis helical winding technique would use fabric of uniformlight-transmitting ability throughout. That is, instead of athree-segment strip of varying opacity, the winding strip could be madeof a single, ultralight, non-woven fabric. In the “open” position, lightwould be filtered through two layers (the front and rear compositefacings), while in the partially and fully closed positions, it would befurther filtered through the vane layer of fabric, causing an additionalfifty percent diminution in the light transmission through the blind. Ifangle-dependent polarizing material were used, further control of thelight transmission could be obtained.

[0085] Because this helical winding process permits use of narrow stripsof material to form the composite facing panels, the face panels can beformed of lace material. Heretofore, continuous sheet facing panels weretoo wide to permit lace to be used at an acceptable price. Also, itwould be difficult to match the pitch of the finished shade to therepeats of the wide-goods lace. As further alternatives, the vaneportion may be a thin wood veneer laminate, or printed cloth withdifferent colors on its opposite sides.

[0086] The modified embodiment of FIG. 18 is similar to the embodimentof FIG. 5, but employs a different means of opacifying the center orvane portion of each strip. These pocketed strips 102 each compriseoverlapping rear and front sheer facings 104, 106, respectively,pre-joined (i.e., prior to winding) by glue lines or ultrasonicjunctions 108. The central overlapping thirds and glue lines define aninsert-receiving pocket 110. Strips 102 are wound and bonded together atglue lines 112, as in the previously described embodiment of FIGS. 5, 9and 10. Later, after cutting open the helically wound tube, opaqueinserts 114 may be inserted in pockets 110 to provide the desired opaquevanes. As a further alternative, the pocketed strips can have the senseof the overlap reversed. That is, front sheer facing 106 can overlaprear sheer facing 104. Alternatively, the individual facing strips 104,106 and a continuous strip of opaque insert 114 can be helically woundtogether by use of multiple feed rolls 72 appropriately positioned tofeed with the desired overlaps onto the winder.

[0087]FIG. 19 illustrates an example of a double-deep structure havingmultiple rows of vanes or central ligaments. Each strip 116 comprisesfive segments, namely, rear, front and central sheer portions 118, 120,122, respectively, and first and second opacified portions 124, 126,respectively. Successive strips are helically wound and bonded togetherat glue lines 128, as previously described. Opacified portions 124, 126could have different degrees of opacity, so that, depending upon whichcolumn of vanes was closed, a light-blocking or a semi-translucent modecould be selected. Alternatively, these two portions could becross-polarized to provide a choice of opacities. With both vanes fullyopen, a transparent light path would be provided through the alignedsheer portions 118, 120, 122.

[0088] By shortening the length of central ligament or sheer portion122, it will “go straight” or taut before the front and rear facings,providing uniform pitch for the hanging blind, and allowing the frontand rear facing segments 118 and 120 to assume a softer, slightly loopedor curving, appearance.

[0089] In an alternative winding process, a multi-lead windingarrangement can be employed. A first such arrangement, illustrated inFIG. 20, introduces a second distinct pre-formed three-portion strip 40b from a separate supply roll 72. For the simplicity of illustration,dancer 73 has been omitted from this Figure, as well as from the furtheralternative illustrated in FIG. 21. A similar pair of glue nozzles 78 bis provided to apply glue stripes to strip 40 b in the same manner andlocation as in the case of the primary strip 40 a. Because the fabricloop or tube 88 is lengthened by two non-overlapping strip portions perrevolution, rather than one, the helix lead angle must be doubled. Thatis, the angle between spars 56, 58 and nip sets 60 and 66 must bedoubled.

[0090] A second multi-feed arrangement is illustrated in FIG. 21.Instead of feeding a pre-formed three-portion strip from supply roll 72,the individual portions of the strip can be fed from separate supplyrolls and joined to each other (with minimal overlap) as they are laidupon and joined to the previously applied winding of fabric tube 88.These junctions are preferably achieved by ultrasonic welding, but gluelines may alternatively be used. In FIG. 21, three supply rollssimultaneously feed separate strip portions 40 a, 40 b and 40 c. Only asingle glue line (from nozzle 78 a) is required to secure portion 40 ato the prior winding or wrap. Similarly, only a single glue line (fromnozzle 78 c) is required to secure central portion 40 c to adjacentportion 40 b of the same wrap. However, two widely spaced glue lines(from nozzles 78 b) are required to join central portion 40 b to portion40 a of the same wrap and to separately join portion 40 b to portion 40c of the prior wrap. Note that two or more strip portions (here,portions 40 a and 40 b) can be fed into the fabric loop at the sameplace, i.e., at nip set 66, with an offset equal to the desired offsetper lap or wrap. A strip portion (here, portion 40 c) can also be fed inat a separate location on the fabric loop, i.e., at nip set 60. As longas the feed-in locations are within the flat portion of the fabric loop88, the offset remains equal to the desired offset per lap in thefinished goods.

[0091]FIG. 23 shows, with the vertical scale exaggerated for clarity, aprior art three-element strip construction used to form the fabricVenetian blind disclosed in U.S. Pat. No. 5,888,639. Strip 130 comprisesan opacified vane portion 132 whose opposite longitudinal edges areultrasonically welded to front and rear sheer strips 134, 136,respectively (each shown as a small “x”), at weld lines 138, 140respectively. The relatively opaque strip is wider than the sheerstrips, and the sheers are aligned with the opposite edges of the opaquestrip. Thus, there is only one sheer present at each edge, allowing athrough-welding of one sheer to each edge of the relatively opaquestrip. This prior art process then subjects the welded three-elementstrip to a series of operations, including edge trimming, opening of thewelded joints (as shown by dotted lines in FIG. 23), and flattening toultimately obtain a flattened, three-element strip. The resulting stripis then cut to a length corresponding with the width of the window intowhich the blind is to be inserted. The cut-to-length strips are then,according to this prior art disclosure, stacked and bonded together,using a technique substantially different from the helical windingtechnique disclosed herein.

[0092]FIG. 24 is a view similar to FIG. 23, but showing a modifiedthree-element strip construction according to one embodiment of thepresent invention. Unlike the three-element strip constructions of eachof FIGS. 6, 7 and 8 of the present invention, and also unlike the priorart configuration of FIG. 23, the construction of three-element strip142 of FIG. 24 comprises a relatively opaque strip 144 to which onesheer strip 146 (which may be the front sheer strip) is lapped slightlythereunder and preferably ultrasonically welded at weld line 148, justas in the embodiment of FIG. 6, while the other sheer strip 150 (whichmay be the rear sheer strip) is aligned with the opposite edge ofrelatively opaque strip 144, and in fully overlapping relationshipthereto, and welded at weld line 152.

[0093] The resulting “half-lapped” three-element strip 142 is thenhelically wound, as shown in FIG. 25, with the double-thick edge ofincoming strip 142 a closer to the previously formed winding 142 b ofthe helix. FIG. 25 is a view generally in the direction of left to rightin FIG. 9, but showing a modified assembly sequence adapted for windingthe half-lapped strip 142. For clarity of illustration only, drive niproll set 60, tension sensing roll 76 and idler roll 162 have beenomitted from FIG. 25. This fragmentary perspective view shows theincoming strip 142 a as it turns over the omitted tension sensing roll76 and idler roll 162 just prior to interfitting with the immediatelypreceding wrap 142 b. As is evident in FIG. 25, the trailing edge of thehelix, namely, the free edge of rear sheer strip 150 b, is temporarilylifted up or partially curled back from underlying opaque strip 144 b bypicker or finger 164 just upstream from the zone where the incomingthree-element strip 142 a is brought into alignment to join thepreviously wound helix. This lifting action permits the double-thickedge of incoming strip 142 a to enter that gap beneath rear sheer strip150 b and slightly overlap relatively opaque strip 144 b.

[0094] The lifting action is accomplished by a finger 164 illustrated inFIGS. 30-31. Only a slight modification to the winding apparatus ofFIGS. 9-10 is required to adapt it to the use of half-lappedthree-element strip 142. The fragmentary perspective view of FIG. 30 istaken generally in the direction of left to right in the unmodifiedapparatus of FIG. 9, but with drive nip roll set 60, tension sensingroll 76 and idler roll 162 (which is added for use with strip 142)omitted for visual clarity only. FIG. 31 is a fragmentary plan view ofthe zone of FIG. 30 where the incoming strip 142 a is engaged by finger164 and interfits with the preceding winding 142 b.

[0095] As compared with the apparatus illustrated in FIGS. 9-10, twostructural changes appear in FIGS. 30-31. First, idler roll 162 has beenadded, to re-direct the infeeding strip so that it has a horizontal runimmediately upstream of nip rolls 62,64. This horizontal run isnecessary so that the incoming and preceding windings can be properlyinterfit with each other for bonding. Second, finger 164 has been addedas an aid in opening up the trailing free edge of rear sheer strip 150 bof the preceding winding so that it can receive the double-thick edge ofincoming strip 142 a.

[0096] Referring to FIGS. 25, 30 and 31, it will be seen that thetrailing free edge of rear sheer strip 150 b is pushed laterally andlifted slightly by finger 164, which is mounted on the end of supportrod 170. To accomplish that shifting, finger 164 has a lower horizontalledge portion 166, shown in dotted lines in the plan view of FIG. 31,which the free edge of sheer strip 150 b rides upon as it moves towardidler roll 162. As a portion of such strip edge is lifted onto ledge166, it is then engaged by a generally vertical leg 168 of finger 164.Vertical leg 168 cooperates with horizontal ledge portion 166 tolaterally shift as well as lift the edge of strip 150 b for a sufficientlongitudinal running length to permit the double-thick edge of incomingthree-element strip 142 a, which is offset from the previously woundwrap 142 b by the helix lead, to overlap the relatively opaque and loweror front sheer portions 144 b and 146 b, respectively, of previouslywound wrap 142 b, and tuck in underneath the lifted edge of upper orrear sheer 150 b.

[0097] Application of front glue line 150 is accomplished by anapplicator (not shown) located immediately above the double-thick,interfitting edge of rear sheer strip 150 a and downstream from idlerroll 162, that is, at a point where the free edge of the rear sheerstrip 150 b of the preceding wrap is still curled back to expose theglue-receiving edge of strip 150 a (see FIGS. 25 and 31). After thatoverlapping relationship is established between the double-thick edge ofincoming strip 142 a and the underlying relatively opaque vane 144 b ofpreviously wound strip 142 b (see FIGS. 25 and 31), the overlappingportion of strip 142 a moves beyond vertical leg 168 of finger 164(i.e., below the finger as viewed in FIG. 31) and returned to aflat-lying condition. The underside of the now lowered free edge of rearsheer strip 150 b will then contact glue strip 156 on the upwardlyfacing edge of incoming rear sheer strip 150 a to permit the requiredbond to be created.

[0098] The horizontal ledge portion 166 of finger 164 may serve anadditional purpose. Where the glue line is shifted away from theunderlying welded joint, as shown in the embodiment of FIG. 27, there isa tendency for the glue to bleed through the underlying sheer andtemporarily form a fragile, weak attachment to the underlying relativelyopaque vane. This unintended attachment would typically break the firsttime that the cells are fully opened, allowing the assembled panel tofunction normally, with the vanes fully free except at their weldedjoints. However, assuring such spontaneous separations occur uniformlyand totally throughout the entire product may require a closer and morecostly control of glue application than otherwise necessary. Thisproblem can be completely avoided by dimensioning ledge portion 166 sothat its left edge (as viewed in FIG. 31) is positioned to separate anytemporary glue attachment resulting from bleed through of glue betweensheers 150 b and 150 c.

[0099] Referring again to FIG. 25, front glue line 154 has already beenapplied to front sheer 146 a of incoming strip 142 a before it makes theturn around roll 76, as shown in the upper right of portion FIG. 25.Thus, glue line 154 will be properly positioned on the lower side of thestrip for engagement with and bonding to preceding front sheer 146 b.Rear glue line 156, however, must be on the upwardly facing side of rearsheer strip 150 a in order to engage and bond to the underside of theuplifted trailing edge of rear sheer strip 150 b. Therefore, theapplicator (not shown) for glue line 156 must be located to apply theglue after the strip has passed roll 76 and before it passes under drivepressure roll 64.

[0100] The resulting helix is cut open, as previously described, and cutto size for particular windows. FIG. 26 shows the end view of theresulting cellular structure in its partially open condition. It isevident that, in contrast to the structures of FIGS. 3-8, the two sheerstrips of a given three-element strip form the front and rear portion ofthe same, rather than adjacent, cells. Significantly, another differenceis that the direction of lapping of adjacent facing segments is the sameon both the front and rear of the resulting panel. That is, e.g., rearsheer segment 150 b overlaps adjacent rear sheer segment 150 a, just asfront shear segment 146 b overlaps adjacent front sheer segment 146 a.This configuration is advantageous in that, if the fabric Venetian blindis mounted so that the overlap is oriented shingle style, both front andrear facing panels will be so oriented, and the exposed sheer edges willless likely to collect dust or fray from contact with downwardlydirected cleaning strokes or falling objects.

[0101] Furthermore, overlaying one of the sheer strips onto the stifferrelatively opaque vane reduces the instability of the three-elementstrip, thereby improving wrap-to-wrap alignment and the smoothness ofthe assembled composite facing panels. This advantage is particularlybeneficial when using extremely fine knits such as diamond tulle, whichis preferred in conjunction with a tricot knit for the opposite facewhen reduction of the moiré effect is desired.

[0102]FIG. 27 shows a modified version of FIG. 26. As in the differencebetween the embodiments of FIG. 22 and FIG. 5, the modification resultsfrom a shifting of the location of glue lines 154′ and 156′. Therelocation of the glue lines away from the weld lines 148, 152,respectively, creates inwardly projecting front and rear sheer tabs 158′and 160′, respectively.

[0103]FIG. 28 shows the same three-element strip structure andorientation as shown in FIG. 25, except that glue lines 154 and 156 havebeen initially applied to the opposite elements of the to-be-bondedsurfaces. That is, front glue line has been shifted from the lower sideof the left edge of incoming front sheer strip 146 a (as shown in FIG.25) to the upper side of the right edge of the front sheer strip 146 b″of the preceding wrap of the helix (as shown in FIG. 28). Similarly,rear glue line 156 in the FIG. 28 illustration is applied to the curledback, upwardly facing, underside of the rear sheer strip trailing edgeof the previously wound three-element strip 142 b″. An appropriatepicker or finger (not shown) would be provided to temporarily curl backand invert that trailing edge of rear sheer strip 150 b″.

[0104]FIG. 29 shows a further modification of the manner of winding thethree-element strip of FIG. 24. In this embodiment, the orientation ofthe strip is reversed, with the double-thick edge of the previouslywound strip trailing rather than leading. Therefore, the free edge ofthe incoming rear sheer strip 150 a′″ must be opened and curled back toreceive rear glue line 156′″ and to permit entry of the double-thicktrailing edge of preceding wound strip 142 b′″, and then uncurled toenclose such trailing edge. This arrangement presents greater alignmentand guidance difficulties, and is therefore not preferred.

[0105]FIGS. 32a-32 b through FIGS. 38a-38 b show additional embodimentsof three-element strips. As in the case of FIGS. 23 and 24, theproportions of the strips in these drawings are exaggerated for clarity,and the location of the weld lines is shown with an “x”. The relativelyopaque vanes are shown with cross-hatching. Within each numbered pair ofdrawings, the “a” Figure shows the three strip portions in theirflattened condition as welded, while the “b” Figure shows thethree-element strip partially opened as it would be in thelight-admitting position within a fabric Venetian blind.

[0106] In the light of the foregoing explanation of the winding andassembly technique employed with the embodiment of FIG. 24, thoseskilled in the art will understand how to wind and assemble thesealternative three-element strip configurations. The embodiments of FIGS.36-42 would require, during the winding operation, a temporary liftingof the previously wound upper sheer free end to allow tucking under theedge of the incoming three-element strip, as described above withreference to FIGS. 25 and 30-31. It will also be recognized that achoice exists as to which element will overlap the other at the requiredglue joints between adjacent three-element strips. That is, by way ofexample, each of the glue joints required for adjacent three-elementstrips according to the embodiments of FIGS. 32-35 can only be made withthe incoming winding as the overlapping element at each joint.Conversely, in the embodiments which are generally Z-shaped, such asFIGS. 38, both free edges of the incoming three-element strip can beeither overlaid or tucked under the corresponding portion of thepreviously wound three-element strip. In the configurations of FIGS. 36and 37, the upper sheer (as shown in the Figures) can only overlap,whereas the lower sheer can overlap or tuck under, as desired.

[0107] The embodiments of FIGS. 39-42 show two-element strips which areformed with a pocket for subsequent insertion of a preferably semi-rigidopaque vane, which vanes are shown in the “b” Figures of each numberedpair. Otherwise, the same winding and assembly considerations asdiscussed above apply.

[0108] As discussed with respect to the embodiment of FIG. 27, each ofthese embodiments of FIGS. 32-42 can be constructed as shown, with theglue line between adjacent windings essentially overlying previouslyformed weld joints in the overlapped winding, or they may have the glueline shifted laterally away from such weld line (as shown in FIG. 27),creating a short, inwardly projecting sheer tab or ligament.

[0109] While the helical winding technique disclosed herein is normallythe preferred technique for assembling the three-element strips into anarray of cells, some circumstances may make it preferable to initiallycut the three-element strips to length and then overlap them instaggered, parallel alignment for joining them together. One suchcircumstance is where the material chosen for the relatively opaquevanes is not suitable for the repeated longitudinal bending experiencedas the strip traverses the various rolls in the disclosed helicalwinding operation. In that event, a cutting and assembling techniquesuch as disclosed in the previously mentioned U.S. Pat. No. 5,888,639may be preferred.

[0110] Another advantage of the constructions disclosed herein is thatthey all lend themselves to simple lap joints, parallel to the plane ofthe facing panels, at the points of attachment of successive strips toeach other. When so joined, the smooth, generally planar character ofthe facing panels is more likely to be maintained at the joints. Lapjoints so constructed and positioned are to be contrasted with theinwardly turned tabs, perpendicular to the facing panels, such asdisclosed in FIGS. 11 and 11a of U.S. Pat. No. 5,888,639, which is moretypical of honeycomb type cellular constructions as shown in FIG. 1 ofthat patent. The latter construction requires an additional folding stepfor assembly, and, unless there are post-assembly creases set at theface joints, it will not lie flat. Furthermore, if it is creased to makethe faces lie flat, the vanes will not lie closed naturally or fully (asdesired) and will not make the desired curving shapes when open.

[0111] Another advantage of the half-lap three-element strip, asexemplified by FIG. 24 and 26 hereof, is that when the strip is spooledinto roll 40 after welding, the double-thick portion is wide and stableenough to make a smooth, uniform roll with no distortion of thematerial. Subsequently, during the winding and gluing steps, this typeof strip has improved directional stability and flatness, resulting in asmoother and more uniform product.

[0112]FIG. 43 illustrates a still further three-element stripconfiguration 172 wherein both front and rear sheer strips are bonded tothe same face of the opacified strip. The term bonded includes anysuitable technique for joining the strip elements together including,but not limited to, gluing, welding and/or sewing. Front sheer strip 176is bonded at 178 to opacified strip 174, while rear sheer strip 180 isbonded at 182 to the opposite end of opacified strip 174.

[0113] In positioning and gluing successive three-element strips inpartially overlapping position, according to the method described withrespect to other embodiments hereof (see FIG. 44), front glue line 184is preferably placed directly over front bond line 178, to minimize anypossible glue bleed-through problems. Rear glue line 186 is preferablyoffset from rear bond line 182, thereby creating a short internal sheertab between rear bond line 182 and rear glue line 186. By way ofexample, front sheer strip 176 may be approximately one andthree-quarters inches in width, rear sheer strip 180 approximately oneand seven-eighths inches in width, and pacified strip 174 approximatelytwo and one-eighth inches in width. With those dimensions, the width ofthe internal sheer tab between rear bond line 182 and rear glue line 186may be about one thirty-second to one sixteenth of an inch. Theresulting sheer tabs are contiguous parts of the sheer composite sheet(180 a+180 b+180 c, etc . . . ) that results from the bonding togetherat rear glue line 186 of adjacent rear sheer strips 180. Any minor gluebleed-through at this rear location creates no problems because thesheer fabric layer in this region are backed only by a steel roll duringthe fabrication process.

[0114] Still further alternatives (not illustrated) for use of athree-element strip similar to the FIG. 43 embodiment could utilize glueline placement to create sheer tabs on the front side of the blindand/or to eliminate the sheer tabs on the rear side.

[0115] This invention may be further developed within the scope of thefollowing claims. Accordingly, the above specification is to beinterpreted as illustrative of only a few operative embodiments of theinvention, and not in a strictly limiting sense. In the followingclaims, the words “right”, “left”, “upper” and “lower” have been used asrelative orthogonal directions for ease of description only, and are notintended to be defined in relation to any external datum, such as thesurface of the Earth. Also, “edge” or “edges”, as used in the claims,means the extreme lateral edges of the strips or strip portion faces,along with a relatively narrow immediately adjacent portion of suchfaces.

I now claim:
 1. A method of forming a light-control panel comprising:providing first and second elongated light-transmitting strip portionsand an elongated, relatively opaque strip portion; orienting said stripportions in a generally parallel array, each strip portion having rightand left longitudinally extending edges and upper and lower opposedfaces; positioning said strip portions so that said first strip portionoverlaps at least a substantial portion of the transverse width of saidrelatively opaque strip portion, and said right edges of said firststrip portion and said relatively opaque strip are substantiallysuperimposed, and so that said left edge of said relatively opaque stripportion overlaps only the right edge of said second strip portion,leaving the remainder of said second strip portion free of overlap bysaid relatively opaque strip portion; and joining said right edge ofsaid first strip portion to said right edge of said relatively opaquestrip, and welding said left edge of said relatively opaque stripportion to said right edge of said second strip portion to thereby forma three-element strip member.
 2. The method of claim 1 which furthercomprises the steps of: positioning longitudinally extending segments ofsaid three-element strip member in partially transversely overlappingand parallel relationship; securing a first segment to an adjacentsecond segment by joining said left edge of said first segment firststrip portion to said right edge of said second segment first stripportion, and by joining said left edge of said first segment secondstrip portion to said right edge of said second segment second stripportion, the secured segments forming an elongated cell having front andrear walls defined by said first and second light-transmitting stripportions of said second segment, said cell further having two additionalwalls defined by said relatively opaque strip portions of said first andsecond segments; and repeating said segment-securing step withadditional adjacent segments to form an extended array of parallelcells.
 3. The method of claim 2 wherein said segment-positioning step isaccomplished by helically winding a continuous length of saidthree-element strip member, with each successive winding segmentpartially overlapping the immediately preceding winding segment.
 4. Themethod of claim 2 wherein said segment-positioning step is accomplishedby cutting said three-element strip member into pieces of predeterminedlengths and then laterally offsetting adjacent pieces by a predeterminedamount.
 5. A method of forming a light-control panel comprising:providing first and second elongated light-transmitting strip portionsand an elongated, relatively opaque strip portion; orienting said stripportions in a generally parallel array, each strip portion having rightand left longitudinally extending edges and upper and lower opposedfaces; positioning said strip portions so that said first strip portionoverlaps a substantial but less than the entire portion of thetransverse width of said relatively opaque strip portion, and said leftedges of said first strip portion and said relatively opaque stripportion are substantially superimposed, and so that said left edge ofsaid second strip portion overlaps only the right edge of saidrelatively opaque strip portion; and bonding said left edge of saidfirst strip portion to said left edge of said relatively opaque stripportion, and bonding said left edge of said second strip portion to saidright edge of said relatively opaque strip portion to thereby form athree-element strip member.
 6. The method of claim 5 which furthercomprises the steps of: positioning longitudinally extending segments ofsaid three-element strip member in partially transversely overlappingand parallel relationship; securing a first segment to an adjacentsecond segment by bonding said left edge of said first segment firststrip portion to said right edge of said second segment first stripportion, and by bonding said left edge of said first segment secondstrip portion to said right edge of said second segment second stripportion, the secured segments forming an elongated cell having front andrear walls defined by said first and second light-transmitting stripportions of said second segment, said cell further having two additionalwalls defined by said relatively opaque strip portions of said first andsecond segments; and repeating said segment-securing step withadditional adjacent segments to form an extended array of parallelcells.
 7. A light-control panel comprising: a first three-element stripincluding a first elongated light-transmitting strip portion having aleft edge bonded to a left longitudinally extending edge of anelongated, relatively opaque strip portion at a first bond line and asecond elongated light-transmitting strip portion having a left edgebonded to a right longitudinally extending edge of said opaque stripportion at a second bond line; a second three-element strip having afirst elongated light-transmitting strip portion having a left edgebonded to a left longitudinally extending edge of an elongated,relatively opaque strip portion at a first bond line and a secondelongated light-transmitting strip portion having a left edge bonded toa right longitudinally extending edge of said opaque strip portion at asecond bond line; a right edge of said first elongated strip portion ofsaid first three-element strip being bonded to a left edge of said firstelongated strip portion of said second three-element strip at a thirdbond line that is substantially directly over the first bond line of thesecond three-element strip; and a right edge of said second elongatedstrip portion of said first three-element strip being bonded adjacent toa left edge of said second elongated strip portion of said secondthree-element strip at a fourth bond line that is offset from the secondbond line of the second three-element strip to form an elongated cell.8. A light-control panel comprising: a first elongatedlight-transmitting strip portion; a second elongated light-transmittingstrip portion; an elongated, relatively opaque strip portion; each stripportion having right and left longitudinally extending edges and upperand lower opposed faces; said first elongated strip portion having aleft edge bonded to the left longitudinally extending edge of saidopaque strip portion; said second elongated strip portion having a leftedge bonded on a right longitudinally extending edge of said opaquestrip portion; and wherein said first and second elongated stripportions are each bonded to a same face of the opaque strip portion.